Does anyone know if an oral notice of non-renewal counts instead of the writing notice by law??

I leased an apartment for 10 months, on the 8 month i asked the landlord if he could give me the apartment cheaper, he told me that the price adjustments and deals were going to come in the mail. I waited and nothing came in the mail, so i went again and ask about any special deals or the prices. The prices were too high so right there i told the leasing office that since the prices were too high that i was not going to renew my contract and that i was going to move out. I never renewed the contract, plus i turned in my key on the day my contract ended (on time). Now the office is charging me a big amount because i didn't notify them i was moving out. Is an oral notice binding, taking in consideration the that i turned in my key on time and i didn't receive a response in the mail promptly before my lease ended??